The invention concerns the feeding of tree trunks to a processing machine by means of centering elements adjustable symmetrically relative to the center feed line, wherein prior to the entry into the processing machine several opposing guide surfaces are cut on the tree trunk, which immediately thereafter enter into contact with guide elements.
Tree trunks, which in processing machines, such as sawing machines and profile molding machines, are to be cut into squared timber, boards and optionally usable chips, must be fed to the processing machine in a straight line, wherein the center feed line is to coincide as accurately as possible with the center line of the tree trunk in order to make possible an optimum utilization of the wood. In the course of the feeding process the swinging motions of the tree trunk must be extensively eliminated, as otherwise the cuts do not follow a straight line.
In order to make possible the straight line feeding of tree trunks to a processing machine, it is known to initially cut guide surfaces on the tree trunk, which extend in a straight line and make possible the straight line guidance of the tree trunk via these guide surfaces. While the presence of such guide surfaces eliminates the difficulties resulting from the conical and usually curving shape of the outer surfaces of the tree trunks as the tree trunk passes through the processing machine, there exists a problem in keeping the tree trunk centered while the guide surfaces are being cut.
In a known process disclosed in German Patent 2921458, the tree trunks are gripped in their central area and at their end by centeringly adjustable clamping tools supported on slides displaceable on a rail. The tree trunk gripped in this manner is fed to milling cutters which mill the guide surfaces by which the tree trunk is subsequently guided by means of guide rolls. As soon as the front end of the tree trunk is taken up by these guide rolls, the center clamping tool opens and the tree trunk is then guided between the guide rolls and by the rear clamping tool. The tree trunk guided and partially processed in this manner is transported to a processing installation, in which the outside of the trunk is milled cylindrically. It is then additionally supported on this cylindrical surface, while the trunk processed on all sides is passed to several forward feed rolls located at in the inlet of a subsequent processing machine, for example a saw.
The apparatus required for this known process is relatively complicated. The longitudinally displaceable slides carrying the clamping tools must be returned into their initial position following the passage of a tree trunk and loaded, before they are able to feed in the next tree trunk. This places narrow limits on the possible rate of operation. To make possible the accurate guidance of the tree trunk at the inlet of the processing machine, the known process requires that the guide surfaces be cut in two successive processing steps, i.e. once for the initial guidance of the front end of the tree trunk, and secondly to obtain the cylindrical outer surface prior to the inlet to the group of guide rolls in front of the processing machine.
It is therefore the object of the invention to provide a process and apparatus which makes it possible to guide tree trunks to a processing machine rapidly and accurately and in a simplified manner.